bcachefs: bch2_bkey_sectors_need_rebalance() now only depends on bch_extent_rebalance

Previously, bch2_bkey_sectors_need_rebalance() called
bch2_target_accepts_data(), checking whether the target is writable.

However, this means that adding or removing devices from a target would
change the value of bch2_bkey_sectors_need_rebalance() for an existing
extent; this needs to be invariant so that the extent trigger can
correctly maintain rebalance_work accounting.

Instead, check target_accepts_data() in io_opts_to_rebalance_opts(),
before creating the bch_extent_rebalance entry.

This fixes (one?) cause of rebalance_work accounting being off.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

fs/bcachefs/inode.h

@@ -285,12 +285,14 @@ void bch2_inode_opts_get(struct bch_io_opts *, struct bch_fs *,
 			 struct bch_inode_unpacked *);
 int bch2_inum_opts_get(struct btree_trans*, subvol_inum, struct bch_io_opts *);
 
+#include "rebalance.h"
+
 static inline struct bch_extent_rebalance
 bch2_inode_rebalance_opts_get(struct bch_fs *c, struct bch_inode_unpacked *inode)
 {
 	struct bch_io_opts io_opts;
 	bch2_inode_opts_get(&io_opts, c, inode);
-	return io_opts_to_rebalance_opts(&io_opts);
+	return io_opts_to_rebalance_opts(c, &io_opts);
 }
 
 int bch2_inode_rm_snapshot(struct btree_trans *, u64, u32);

fs/bcachefs/opts.h

@@ -659,18 +659,4 @@ static inline void bch2_io_opts_fixups(struct bch_io_opts *opts)
 struct bch_io_opts bch2_opts_to_inode_opts(struct bch_opts);
 bool bch2_opt_is_inode_opt(enum bch_opt_id);
 
-/* rebalance opts: */
-
-static inline struct bch_extent_rebalance io_opts_to_rebalance_opts(struct bch_io_opts *opts)
-{
-	return (struct bch_extent_rebalance) {
-		.type = BIT(BCH_EXTENT_ENTRY_rebalance),
-#define x(_name)							\
-		._name = opts->_name,					\
-		._name##_from_inode = opts->_name##_from_inode,
-		BCH_REBALANCE_OPTS()
-#undef x
-	};
-};
-
 #endif /* _BCACHEFS_OPTS_H */

fs/bcachefs/rebalance.c

@@ -121,12 +121,10 @@ u64 bch2_bkey_sectors_need_rebalance(struct bch_fs *c, struct bkey_s_c k)
 		}
 	}
 incompressible:
-	if (opts->background_target &&
-	    bch2_target_accepts_data(c, BCH_DATA_user, opts->background_target)) {
+	if (opts->background_target)
 		bkey_for_each_ptr_decode(k.k, ptrs, p, entry)
 			if (!p.ptr.cached && !bch2_dev_in_target(c, p.ptr.dev, opts->background_target))
 				sectors += p.crc.compressed_size;
-	}
 
 	return sectors;
 }
@@ -140,7 +138,7 @@ static bool bch2_bkey_rebalance_needs_update(struct bch_fs *c, struct bch_io_opt
 	const struct bch_extent_rebalance *old = bch2_bkey_rebalance_opts(k);
 
 	if (k.k->type == KEY_TYPE_reflink_v || bch2_bkey_ptrs_need_rebalance(c, opts, k)) {
-		struct bch_extent_rebalance new = io_opts_to_rebalance_opts(opts);
+		struct bch_extent_rebalance new = io_opts_to_rebalance_opts(c, opts);
 		return old == NULL || memcmp(old, &new, sizeof(new));
 	} else {
 		return old != NULL;
@@ -163,7 +161,7 @@ int bch2_bkey_set_needs_rebalance(struct bch_fs *c, struct bch_io_opts *opts,
 			k.k->u64s += sizeof(*old) / sizeof(u64);
 		}
 
-		*old = io_opts_to_rebalance_opts(opts);
+		*old = io_opts_to_rebalance_opts(c, opts);
 	} else {
 		if (old)
 			extent_entry_drop(k, (union bch_extent_entry *) old);

fs/bcachefs/rebalance.h

@@ -4,8 +4,28 @@
 
 #include "compress.h"
 #include "disk_groups.h"
+#include "opts.h"
 #include "rebalance_types.h"
 
+static inline struct bch_extent_rebalance io_opts_to_rebalance_opts(struct bch_fs *c,
+								    struct bch_io_opts *opts)
+{
+	struct bch_extent_rebalance r = {
+		.type = BIT(BCH_EXTENT_ENTRY_rebalance),
+#define x(_name)							\
+		._name = opts->_name,					\
+		._name##_from_inode = opts->_name##_from_inode,
+		BCH_REBALANCE_OPTS()
+#undef x
+	};
+
+	if (r.background_target &&
+	    !bch2_target_accepts_data(c, BCH_DATA_user, r.background_target))
+		r.background_target = 0;
+
+	return r;
+};
+
 u64 bch2_bkey_sectors_need_rebalance(struct bch_fs *, struct bkey_s_c);
 int bch2_bkey_set_needs_rebalance(struct bch_fs *, struct bch_io_opts *, struct bkey_i *);
 int bch2_get_update_rebalance_opts(struct btree_trans *,